Space debris is man-made objects that are orbiting in geocentric orbits without being used. Examples of space debris include: spacecrafts (artificial satellites, space stations, space shuttles, and the like) which terminated operations due to end of lives, accidents and failures; bodies and components of rockets used to launch artificial satellites; fragments generated in stage separation of multistage rockets; tools dropped by astronauts during extravehicular activities; and the like. Moreover, the space debris also includes minute debris generated by space debris colliding with each other and being crushed into pieces. Accordingly, there are various sizes of space debris.
The above-described space debris may collide with a currently operating spacecraft in a geocentric orbit intersecting the geocentric orbits of the space debris and may hinder operation of the spacecraft. Existence of large space debris (including intact spacecrafts) having diameters in excess of 10 cm can be detected from the ground in advance by using radars and the like, and the spacecraft can be caused to take measures for evasive actions (orbit change, posture change, crew evacuation, and the like). However, since small space debris having diameters equal to or below 10 cm is difficult to detect from the ground, it is practically impossible to cause the spacecrafts to take evasive actions.
Accordingly, as a countermeasure for the space debris, there is proposed a technique in which: a thin metallic plate is located in front of a spacecraft in a traveling direction; space debris flying toward the spacecraft is made to hit and penetrate this metallic plate; and thus the space debris is crushed into small pieces. In this technique, the space debris after the crush, which have an increased area-to-mass ratio (average cross-sectional area/mass) as compared to that of the space debris before the crush, is dropped from the geocentric orbit by means of air drag (atmospheric drag) (see Patent Document 1).